Environment and Radar Operation Simulator

The environment and radar operation simulator (EROS) is a hardware system whose function is to produce realistic synthetic radar backscatter, incorporating both target and clutter. The simulator is electrically connected to a subject radar and responds in real time to the radar's antenna scan angle by producing the correct composite video signal.     

The role of magnetic field shear in solar flares

We present observational results and their physical implications garnered from the deliberations of the FBS Magnetic Shear Study Group on magnetic field shear in relation to flares. The observed character of magnetic shear and its involvement in the buildup and release of flare energy are reviewed and illustrated with emphasis on recent results from the Marshall Space Flight Center vector magnetograph. It is pointed out that the magnetic field in active regions can become sheared by several processes, including shear flow in the photosphere, flux emergence, magnetic reconnection, and flux submergence. Modeling studies of the buildup of stored magnetic energy by shearing are reported which show ample energy storage for flares. Observational evidence is presented that flares are triggered when the field shear reaches a critical degree, in qualitative agreement with some theoretical analyses of sheared force-free fields. Finally, a scenario is outlined for the class of flares resulting from large-scale magnetic shear; the overall instability driving the energy release results from positive feedback between reconnection and eruption of the sheared field.     

Charge exchange lifetimes for ring current ions

In applying the charge exchange mechanism to ion phenomena within the Earth's magnetosphere it is critical to the proper interpretation of observations that the charge exchange lifetimes for the ions be known as accurately as possible. Various new results have been published which significantly modify the charge exchange lifetimes which have been used in space physics research during the past decade and a half. Some of the newer results have been used in the application of the charge exchange decay mechanism but the use has been limited and for the most part incomplete. The neutral hydrogen density distribution now yields lifetimes which are shorter than previously calculated, while the functional dependence of the lifetimes on pitch angle provides for slower decay for ions mirroring off the geomagnetic equator. This review coalesces and summarizes the latest and best measurements of the physical quantities involved in the complete calculation of the charge exchange lifetime of the mirroring magnetospheric ions.     

The variability of the sun's ultraviolet radiation

The intensity of continua and emission lines which form the solar UV spectrum below 2100 Å is variable. Continua and emission lines originating from different layers in the solar atmosphere show a different degree of variability. Coronal emission lines at short wavelengths are much more variable than continua at longer wavelengths which originate in lower layers of the solar atmosphere. Typical time-scales of solar UV variability are minutes (flare induced), days (birth of active regions), 27 days (solar rotation), 11 years (solar cycle) and perhaps centuries, caused by long-term changes of the solar activity. UV intensity variations have been determined by either absolute irradiance measurements or by contrast measurements of plages vs. the quiet sun. Plages are the main contributor to the solar UV variability. Typical values for the solar UV variability over a solar cycle are: <1% at wavelengths longer than 2100 Å, 8% at 2080 Å (continuum), 20% at 1900 Å (continuum), 70% at H Lyα, 200% in certain emission lines 1200 < λ < 1800 Å and more than a factor of 4 in coronal lines λ < 1000 Å. Plage models predict the variable component of the solar UV radiation within ±50%. Absolute fluxes are known within ±30%. Several efforts are underway to monitor the solar UV irradiance with a precision better than a few percent over a solar activity cycle.     

Siple VLF transmissions and their magnetospheric effects observed at Halley,Antarctica

Halley (75.5°S, 26.7°W, L = 4.3) is well placed for reception of subionospheric signals from the Siple transmitter. Occasionally a two-hop magnetospheric response to such signals can be observed. The data presented here are relevant to the problems of the radiation and propagation of VLF waves in the polar earth/ionosphere waveguide, duct stimulation and ducted wave amplification and the growth of triggered emissions. An upper sideband emission 20–40 Hz higher in frequency than the transmitted pulse was often received at a similar strength to, and simultaneously with the two-hop whistler mode echo.     

Responses of the upper middle atmosphere (60–110 km) to the stratwarms of the four pre-map winters (1978/9–1981/2)

The global developments of the four stratospheric events (～20–50 km) are described, using balloon, satellite and rocket data. Winds data for heights of 60–95 km, derived from L.F. drift (52°N, 15°E; Europe) and M.F. radar (52°N, 107°W; Canada), are then compared with the stratospheric data. There is clear evidence that the preliminary planetary waves often penetrate strongly to ～90 km, and that mean wind reversals also occur. However, there are dramatic differences between European and Canadian mesospheric responses.     

The giant planets and their satellites: Report on the Cospar Symposium,Ottawa, Canada,May 18–21, 1982

A $\text{Symposium on the Giant Planets and Their Satellites}$ was presented in conjunction with the Twenty-fourth Plenary Meeting of the Committee on Space Research. This paper summarizes the talks presented and places the remaining papers of this volume in context.     

Heavy ion action on yeast cells: inhibition of ribosomal-RNA synthesis, loss of colony forming ability and induction of mutants.

The action of heavy ions (Ar to U) accelerated to specific energies up to about 10 MeV/u (u=atomic mass unit) on different functions of yeast cells was studied. Ribosomal-RNA synthesis is inhibited according to a single-hit mechanism. Inactivation cross-sections were linearly related to the ratio of the squares of the effective charge Z* and the velocity of the ions. It is concluded from the analysis that the range of the most energetic delta-electrons is larger than previously assumed. There is no such dependence for survival and induction of mutants. In both cases cross-sections increase with the ion's specific-energy indicating an important contribution of long-range delta-electrons. The analysis shows that diploid yeast is not killed by a single-hit mechanism even by very heavy ions if the track width is too small. The relative importance of the penumbral region is even more pronounced with the more sensitive strains.     

IUE and Einstein observations of supernovae

In this paper IUE observations of two type II and three type I Supernovae (see Table I and Table II) are reviewed. The type II events were also observed by Einstein and SN 1980k was detected in the soft X-ray energy band. Combining UV spectra available of the same events one has the elements to construct a physical picture which accounts for all observations. For the type II events it appears that the progenitor star was a massive supergiant which underwent a severe mass loss before becoming Supernova. For the type I events there is neither X-ray nor, for the time being, radio detection. The high similarity of the optical and UV spectra for the three events indicates that type I Supernovae are the end products of one and the same phenomenon.     

WAMDII — A wide angle Michelson Doppler imaging interferometer for spacelab

A CCD imaging device has been designed which combines a spatial resolution of 0.1° with a spectral resolving power of 10⁵, sufficient to measure Doppler shifts and line widths of individual atmospheric emission lines. It will be flown aboard Spacelab and will be used to study neutral winds and temperatures as functions of height, latitude and time of day.